Relativity is the idea that a measurement depends on the observer. Einstein's relativity, general relativity, the theory of relativity.
Special relativity, published in 1905, holds that the speed of light is the same for every observer and that time and length are not. General relativity, from 1915, describes gravity as the curving of spacetime by mass. Both are confirmed to extraordinary precision, and satellite navigation would fail within minutes without correcting for them.
1nounrelativityThe physical theory that measurement depends on the observer.
“General relativity dates from about 1915.”
relativity is a physical theory.
Relative plus -ity, and the physical sense translates the German Relativität used in the work of Einstein and his contemporaries.
German
Relativität — relativity
English, today
relativity
From relative + ity. Sense 2.1 (“reliance of the nature of physical phenomena on the relative motion between an observer and the thing observed”) is a translation of German Relativität (“relativity”) used in the worksFor example, {{cite-journal|author=A[lbert] Einstein|authorlink=Albert Einstein|title=
Etymology from Wiktionary, CC BY-SA